This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A302006 #4 Mar 30 2018 12:50:09 %S A302006 8,128,1808,25808,368144,5251712,74917424,1068722240,15245681888, %T A302006 217484775440,3102493407248,44258111045072,631356826964288, %U A302006 9006517303652528,128480995970256128,1832824583461859168 %N A302006 Number of nX4 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A302006 Column 4 of A302010. %H A302006 R. H. Hardin, <a href="/A302006/b302006.txt">Table of n, a(n) for n = 1..210</a> %F A302006 Empirical: a(n) = 13*a(n-1) +18*a(n-2) +a(n-3) -4*a(n-4) %e A302006 Some solutions for n=5 %e A302006 ..0..0..0..1. .0..0..0..0. .0..0..0..1. .0..0..0..1. .0..0..0..0 %e A302006 ..1..0..1..0. .0..1..1..0. .1..1..0..0. .1..1..0..0. .1..1..1..1 %e A302006 ..0..0..1..0. .0..1..1..0. .1..1..0..0. .1..0..1..1. .1..0..1..1 %e A302006 ..0..0..1..0. .0..1..0..0. .1..0..1..1. .0..0..1..1. .0..0..0..1 %e A302006 ..0..1..0..0. .1..1..0..0. .1..1..1..1. .0..1..0..0. .1..1..1..0 %Y A302006 Cf. A302010. %K A302006 nonn %O A302006 1,1 %A A302006 _R. H. Hardin_, Mar 30 2018